This proposal is for continuation of a program for producing appropriately purified and carefully assayed preparations of erythropoietin for distributing them to qualified investigators for use in research, and for continuing to investigate methods for more efficient isolation, purification and assay of human erythropoietin. The goal of this project is to ensure the continued availability to investigators of a variety of erythropoietin preparations for uses including the following: Clinical tests of erythropoietin and preparatory animal experimentation, studies involving erythroid cell (BFU-E, CFU-E) clonogenic assays, study of the biochemical and immunological nature - cellular sites of action - mechanism of action of human erythropoietin - development of new purification procedures and assay methods. A laboratory shall be maintained to receive crude preparations of human erythropoietin from the urine of anemic individuals as collected from various populations. This material will be refined and fractionated by biochemical procedures established in this laboratory. The resulting preparations will be carefully characterized with respect to their contents of erythropoietin by in vivo and cell culture assays and when appropriate also with respect to other hematopoietic stimulators such as colony stimulating activity and thrombopoietin. The necessary assay methodology will be further developed. Stocks will be kept on inventory and dispensed to qualified investigators according to the directions of the NHLBI.